Fluid-pressure-actuated tool



June 7, 1927.

E. H. SHAFF FLUID PRESSURE ACTUATED TOOL Original Filed Oct. 27, 1920 Patented June 7, 1927.

UNITED STATES PATENT OFFICE.

ERNEST H. SHAFF, OF GRAND HAVEN, MICHIGAN, ASSIGNOR TO WILLIAM H. KELLER, INC., OF GRAND HAVEN, MICHIGAN, A CORPORATION OF MICHIGAN.

FLUID-PRESSURE-ACTUATED TOOL.

Application filed October 27, 1920, Serial No. 419,793. Renewed October 21, 1926.

My invention relates to fluid-pressure actua-ted tools of the'general type disclosed and claimed in my copending application, Serial No. 371,445 filed April 5, 1920.

One object of the invention is to increase the quickness and reliability with which the valve may be shifted forward on the return stroke.

I accomplish this object by providing an arrangement in which there is no tendency to develop any pressure in the valvechamber used for shifting the valve at the end of the return stroke until it is time to shift the valve.

Further objects and advantages of my invention will become apparent as the description proceeds. I V

In thcaccompanying drawings, Figure 1 is a section of a fluid-prcssure-actuated tool illustrating the application of my invention thereto, and Fig. 2 is a section of part of the tool taken in a. plane approximately at right angles to that of Fig. 1.

In the embodiment of my invention selected for illustration, the tool comprises, briefly, a body member 10 defining-a cylinder in which the piston 12 reciprocates to strike a suitable working tool 14; avalve casing comprising annular memhers 16 and 18 supporting and guiding the valve 20, and a head 22 threaded onto the body and locked in assembled position by a locking clip 24. A supply of pressure fluid is delivered under the control of the operator through passage 26 to an annular chamber 28. I

With the valve in the position shown in Fig. 1 live motive fluid enters through radial passages 30 'terminating in. the annular groove 32 and forces the piston forward to strike a blow against the working tool 14. The dead air in front of the piston flows from the front end of the tool through one or more passages 34 to the annular groove 36 in the valve casing which, as shown in Fig. 1, is in communication with the exhaust groove 38, from which exhaust groove passages 40 opening under the clip 24 allow the fluid to escape into the atmosphere.

In its forward movement the piston toward the end of its stroke covers one orv more passages 42 and uncovers the end of a passage 44. When this occurs, hve motive fluid flows through passage 44 and enters the large valve chamber 46 thereby throwing the valve back immediately to the position shown in Fig. 2.

The air in the chamber back of the valve flange may escape through passage 47 into exhaust passages 40. During this rearward movement of the valve live motive fluid fills the passages 42 which, after passage 44 has been cut oft from the large valve chamber 46, continues to exert pressure on the valve and hold it in its rearmost position.

The movement of the valve tothe position shown in Fig. 2 covers groove 32 to cut off the flow of live motive fluid to the cylinder, and uncovers the exhaust groove 38 so that the rear portion of the cylinder is in direct communication with the atmosphere. It also uncovers the end of a passage 39 putting it into communication with groove 36 and passages 34. Passage 39 receives live motive fluid from the annular chamber 28, which fluid is delivered from passages 34 to the front end of the cylinder to return the piston. On account of the relatively-small size of passage 39, the pressure during the return stroke will be considerably less than the full line pressure. A passage 48 is provided leading from the annular chamber 28 and opening directly into the cylinder at 50. Another passage 52 opens into the cylinder at 54 in close proximity to the opening in the first mentioned passage 48 so that the piston when it covers theends of both passages will connect them together to form a single passage leading from the annular chamber 28 to the small valve chamber 56. When this occurs, live motive fluid is immediately delivered to the small valve chamber 56 to shift the valve forward.

This occurs against the pressure existing at the instant in the large valve chamber 46 which is the same as the pressure in the front end of the cylinder by reason of passages 42 which are continually in communication with the large valve chamber and the front end of the cylinder. As soon as the valve has shifted, however, the front end of the cylin- 'der is again connected to the exhaust passages through passages 34 so that during the forward stroke the pressure in the large valve chamber will be practically atmosloo pheric and the valve will be held firmly in the position shown in Fig. 1.

The rate of flow of fluid through the passage is determined by a plug 58 at the end of the passage which may have an opening of any desired size. Passage 48 lies entirely in the body 10 and may be easily formed by drillinga radialhole, and a longitudinal hole intersecting it, and then closing the outer end of the radial hole by a plug 60. Plugs 58 and 60 may be fastened in place in any desired manner, as,'for instance, by pressing them into place and riveting over the edges of the hole.

Because there is no pressure in the small valve chamber 56 in excess of that in the rear end of the cylinder during the return stroke, the pressure returning the piston may be decreased to a lower point toward the end of the stroke than has heretofore been possible, as this pressure determines the pressure in the large valve chamber 46 which is relied on to hold the valve in its rearmost position until the proper time. The diminution in this pressure, in combination with the change from no pressure at all to full line pressure when thepiston covers the openings at 50 and 54 makes possible a much more certain forward shifting movement of the valve.

The valve should be thrown forward on the return stroke at such a time that live motive fluid entering from chamber 28 will receive and cushion the piston bringing it to rest at the end of the cylinder, immediately throwing itforward again on the next stroke.

The energy stored in the piston at the end of the return stroke will obviously vary greatly with the size of the tool and the length of the stroke, and as the energy increases the valve must be shifted sooner so as to oppose the movement of the piston with full line pressure at a greater distance from the end of the return stroke in order to bring it to rest at the proper point. If the valve shifts too soon the piston will not come all the way back and the force of the next stroke will be diminished, and if the valve Shifts too late the piston will be allowed to strike the end of the cylinder. By the construction illustrated it is possible to vary the time of shifting the valve so as to receive the piston properly for tools having strokes of varying length by varying the size of the aperture in plug 58. It will thus be apparent that for an entire series of tools of different sizes the same identical construction of the valve.

- valve chamber and the valve chamber end of the body may be employed and that at the same time a precise ad ustment may be obtained so as to secure the best efiiciency in operation for each size.

WVhile I have illustrated and described in detail the preferred embodiment of my invention, it should be clearly understood that the disclosure is merely for purposes of illusber slidable in said easingand adapted to receive the rear end of the piston, said valve having large and small pressure areas formed on its outer periphery, and means for automatically shifting the valve member comprising a passage formed in the valve casing exteriorly of the valve member and communicating at one end with the small pressure area of the valve member and at its other end with the interior of the'cylinder forwardly of the valve member, and a second passage formed in the rear end of the cylinder and communicating at its rear end with a source of pressure fluid supply and opening at its forward end into the piston chamber adjacent the forward end of the first mentioned passage, said passages at their adjacent ends being arranged to b controlled by the piston.

2A pressure-fiuid-actnated tool comprising, in combination, a cylinder having apiston reeiprocable therein, avalve casing located at the rear end of the cylinder in alinement with the piston chamber, a valve memberslidable in said casing and adapted to receive the rear end of the piston, said valve having large and small pressure areas formed on its outer periphery, and means for automatically shifting the valve member comprising a passage communicating at one end with the small pressure area of the valve member and at its other end with the interior of the cylinder forwardly of the valve member, and a second passage of relatively smaller capacity communicating at its rear end with a source of pressure fluid supply and opening at its forward end into the piston chamber adjacent the forward end of the first mentioned passage, said passages at their adjacent ends being arranged to be controlled by the piston.

3.111 a pressure-fluid-actuated tool, the combination with a valve, of means including a restricted passage for moving the tool piston rearwardly, means for shifting the valve member forwardly in the rearward movement of the piston comprising a small pressure chamber, a passage constantly communicating at one end with a source of'pressure fluid supply and opening into the cylinder so as to be controlled by the piston substantially before it reaches the end of its return movement, a second passage communicating with the small pressure chamber and opening into the piston chamber adjaa passage opening into the front end of the cent the aforesaid passage, and means for cylinder and connected to said large pres-- holding the valve in its rear position during sure chamber. 10 the rearward travel of the piston until com- In testimony whereof, I have hereunto set munication between said two passages is my hand.

established by the piston including a large pressure chamber onthe valve member and I ERNEST H. SHAFF. 

